0
Check Engine Light
The check engine light comes on in a car when the engine is experiencing a problem. Ask questions here about your car's check engine light.
7,238 Questions
65
How do you check a bit is on or off?
To determine if a specific bit within a bitset is on or off, use the bitwise AND operator. Note that a bitwise AND is not the same as a logical AND.
Logical AND (or &&) is used in Boolean logic:
x && y is true when x and y are both true, otherwise it is false.
Bitwise AND (or &) compares each corresponding bit, returning a value that indicates which bits are set in both values. This is best seen when the two values are placed one above the other so we can compare the corresponding bits:
10101100 &
10110101 =
10100100
From this we can see that the 3rd, 6th and 8th bits are set in both values.
Knowing this, we can determine the state of any individual bit in any value by simply bitwise ANDing the value with the specific bit we are looking for. If the result is zero, then the bit is not set but if the result is nonzero, then it is set.
As an example, let us suppose we want to test if bit 4 is set. Note that bit 4 is not the same as saying the 4th bit. Bit 4 is actually the 5th bit because bit 0 is always the least significant bit in binary. The reason is that bit 0 represents 2 raised to the 0th power which is 1 in decimal or 00000001 in binary. Bit 4 therefore means 2 raised to the 4th power which is 16 decimal or 00010000 in binary.
In decimal notation, we can determine if bit 4 is set in variable named x like so:
x = 181;
if ((x & 16) == 0)
{
// bit 4 is not set
}
else
{
// bit 4 is set
}
Normally it is easier to use hexadecimal notation as it makes it more obvious we are performing a bitwise operation upon binary values rather than decimal values (which is notationally confusing). Given that 16 is 0x10 in hexadecimal, we then get:
x = B5;
if ((x & 0x10) == 0)
{
// bit 4 is not set
}
else
{
// bit 4 is set
}
Note that ((x & 0x10) == 0) is the same as saying (!(x & 0x10)) while ((x & 0x10) != 0) is the same as saying (x & 0x10). The latter is notationally simpler, thus it often makes more sense to reverse the logic:
x = 0xB5;
if (x & 0x10) // read as: if (x & 0x10) is nonzero
{
// bit 4 is set
}
else
{
// bit 4 is not set
}
If we suppose that x is 0xB5 (181 decimal), then we can see more clearly how this works by examining the binary notation:
0xB5 : 10110101 &
0x10 : 00010000 =
0x10 : 00010000 (non-zero, so bit 4 is set)
If we now suppose that x is 0xA5 (165 decimal), then we get:
0xA5 : 10100101 &
0x10 : 00010000 =
0x00 : 00000000 (zero, so bit 4 is not set)
Note that when we're only checking for one bit and that bit is set, the return value is always the same value as the bit we are actually checking for. But when we check for more than one bit (as per the original example at the top of this answer), the result is either zero (none of the bits are set), or some combination of the bits we were looking for (one or more of the bits are set). Therefore it's easier to say the result is either zero or non-zero regardless of how many bits we're checking for.
Another notation we often encounter is the following:
x = 0xB5;
if (x & (1<<4))
{
// bit 4 is set
}
else
{
// bit 4 is not set
}
It looks more complex at first, but it is actually more readable than the hexadecimal notation. 1<<4 is a bit-shift left operation that shifts a 1 four bits to the left (>> would shift to the right). 1 in binary is 00000001, thus if we shift left 4 times we get 00010000. Thus 1<<4 is effectively the same as saying bit 4. By the same token, 1<<7 would mean bit 7 while 1<<2 would mean bit 2. Expressing ideas directly in code like this means we don't need to comment our code so much; it becomes self-documenting.
Note that bit-shifting like this only works when we're only interested in a single bit. However, knowing that we can shift bits left or right means we can more easily determine the status of every bit using a simple for loop:
x = 0xB5;
for (i=0; i<8; ++i) // assumes x is an 8-bit value
{
if (x & (1< { // bit i is set } else { // bit i is not set } } If we want to output the individual bits to a character stream such as standard output, we need to work in reverse, starting from bit 7: x = 0xB5; b = 1<<7; // bit 7 while (b) { if (x & b) { std::cout << '1'; // note: << means 'insert' in this context } else { std::cout << '0'; } b = b>>1; // bit-shift right } std::cout << std::endl; Note that languages like C++ allow the same operator to perform different operations depending on the context. Hence << can be used to bit-shift a value or to insert a character into a character stream. Re-using symbols according to their context like this helps keep the number of symbols to a minimum. C++ also allows us to write the same code in a more concise form: x = 0xB5; b = 1<<7; while (b) { std::cout << (x & b ? '1' : '0'); b = b>>1; } std::cout << std::endl; Of course, there is an even easier way to print an 8-bit binary value in C++: x = 0xB5; std::bitset<8> b (x); std::cout << b << std::endl;
A flashing service light (called a MIL or malfunction indicator lamp) indicates misfiring has been detected. DO NOT DRIVE THE CAR $$$$$. Get the misfiring repaired, could be bad coil or coil packs, bad wires, bad plugs. Driving with misfire can destroy the catalytic converter.
Is there a trick to turn off the service engine soon light on a 99 Saturn Sc-1?
For most Saturns there is a button inside the under-hood fuse panel. With the key on and the engine off, press the button for 15 seconds and it should clear the code... I think. I have to refer to the manual whenever I do that so you may have to do the same.
How do you disable the check engine chime on my 2008 pt cruiser?
The chime can not be disabled or removed.
How do you reset the service engine light on a 2002 GMC Envoy after repair?
Stepping 3 times on the accelerator pedal while in 'run" mode will reset the "Oil Change Light" but not the "Check Engine Light". Still looking for the answer...!
AnswerMost of the OBD2 code scanners have the ability to clear a code. You can usually borrow, rent or buy an OBD2 code scanner from most auto parts retailers. AnswerWell I don't know if this will work on this model but this worked on similar full-sized trucks of the same time frame. Turn the key to run but do not start engine. While in "run" mode step on the accelerator pedel (3)three times then start engine. Couldn't hurt to try it. R.W.if its ses light remove battery ground cable for 30se.
ETS means ENHANCED TRACTION SYSTEM. You need to have the ECU scanned and see what codes come up. With these codes an expert can diagnose the cause of the problem.
Check engine code 1990 Mazda 323?
1990 Mazda 323:The check engine light intermittently flashes a series of long and short intervals. A long flash is followed by 5 short flashes. Then another long flash is followed by 7 short flashes, a pause, and 9 more short flashes. How should I interpret this code?
personally I would check all your hoses to make you have proper pressure....just for the simple fact that if you did have a leak somewhere in the system...it would probably be enough to set off a sensor, well lets face it...it doesn't take much to trip a sensor. Hope I could help!
What fuse is for the check engine light?
The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to a parts store or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.
There isn't a magic fuse that will turn the light off.
There is another problem. If the code is about the purge valve/system the problem could be a broken vacuum line or electrical connection.
this is a generic fault code which stands for, ambient air temperature sensor range/performance.
What can be cause of fault code p0172?
In my 98 Saturn SW2, P0172, system too rich, was caused by a bad engine coolant temp sensor. This is a common failure in these vehicles.It's cheap and easy to replace, and worth trying. When you take it out, if it's the original, it will be cracked. The new ones are metal. It takes a 13mm deep socket.
Could a fuse car a check engine light to come on?
It is possible, but usually fuses fail for a reason
Why would the check engine light of a 1992 firebird come on after 1 mile?
The SES light reports any issue sent to it from the myriad of sensors throughout the car. If the light goes out it means that the condition has cleared. It's obvious that at start up the condition does not exist but only shows itself once the car has warmed up a bit and has been driven. Have the computer scanned; lookup the code and repair whatever may be causing the condition.
How do you reset engine light 190?
The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to AutoZone or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.
When the cause has been repaired the codes can be reset with a scan tool.
How do you reset the 1995 Toyota Avalon check engine light?
I'm by no means a mechanic nor claim to be but, I had the check engine light come on in my 2003 Tacoma - at the same time for a non related issue, I had to replace the battery. By pulling the battery, it removed the power and the check engine light shut off and has not come on since.
I spoke to the dealership regarding and they mentioned that the engine light may not be on, but is still in the memory of the chip and trucks history if it were to be accessed for an inspection or general purposes for the dealership.
Can a car be diagnosed even when the check engine light turns off?
yes it can. if the check engine light shuts off by itself then chances are either the trouble code is a soft code. A hard code will keep the check engine light on until the problem is fixed and the check engine light is reset.
What are the reasons of malfunction?
Malfunctions can occur due to several reasons, including mechanical failure, electrical issues, software bugs, or operator error. Environmental factors such as temperature fluctuations, moisture, and dust can also contribute to equipment failure. Additionally, lack of maintenance or improper usage can exacerbate wear and tear, leading to malfunctions. Regular inspections and maintenance can help mitigate these risks.
underneath the cup holder
Why would a Air bag light came on along with a check engine light?
Crazy as it sounds it could be a voltage problem. You might get an abs light as well. Check the alt voltage for 13.5 or better. If its good you have a real problem and need to get a code reader.
